ABOUT 100,000 CHINOOK salmon hitched a free ride to Tiburon Wednesday aboard the fishing vessel "Merva W," keeping them away from predators that could have thinned their ranks on the journey from the Sacramento River.

The California Department of Fish and Wildlife is in the third year of a project to help the state's salmon fishery and the safe passage experiment was the latest wrinkle in the efforts. They were loaded on the boat Tuesday in Rio Vista and headed south.

"It's a safe, free ride," said Andrew Hughan, spokesman for the department, as he stood along the waterfront at the Romberg Tiburon Center for Environmental Studies.

"They do not have to deal with the predators: no stripers, no seagulls, no sea lions," he said. "They also don't have to deal with the Delta pumps, tides and currents. There are a million hazards. We are cutting out 100 miles of a migration for a 6-inch fish."

And all the while, in their holding tank, the 5-month-old smolts were exposed to the waters the boat plied. That is important because salmon are able to return to the areas where they were born by recognizing the waters through scent, a process know as "imprinting." When they return they spawn and the lifecycle begins anew.

"We need to know more about imprinting," said Brooke Halsey, head of the Tiburon Salmon Institute, which is involved in the project. "The boat cycles the local waters every 12 minutes into the tanks, so we want to see if that imprints the fish so they can find their way home. It's like dropping bread crumbs."

The fish came from the Feather River Hatchery in Oroville.
A second group of 100,000 chinook from the same hatchery were trucked to the Tiburon site Wednesday morning. They were loaded on the "Merva W" through a set of tubes connected to a modified milk truck. It took less than a minute for the fish to be emptied from the truck.

"They are the control group that have not been imprinted," Hughan said. "We want to see if we skip the imprint process, can they still find their way back."

Both groups were later taken out and released on the high tide at the Golden Gate, where they were swept out into the open sea. As they return in late 2016 as adults, computer tags — smaller than pencil lead — will tell scientists if a fish was part of the group from the boat or truck. Data collected over the next few years will be evaluated to determine what methods provide higher survival rates.

"If we can increase the return rate, we give them a better chance at survival," Hughan said, noting human efforts produce about 30 million salmon a year in the state. "If we didn't get involved in salmon production there wouldn't be a recreation commercial fishing season."

The salmon industry in the state is valued at $300 million annually and creates about 2,900 jobs, according to the department.

"It's a huge part of the economy as well as our environment," Hughan said.